The present invention relates to a glass having the optical characteristics n.sub.D =1.630.+-.(1.5.multidot.10.sup.-2) and v.sub.D =59.5.+-.1.0. Glasses having these optical characteristics are known (see for instance DE-PS No. 14 21 877=U.S. Pat. No. 3,248,238), whose disclosures are incorporated by reference herein). However, they all contain a high percentage of BaO and consequently have very little chemical stability.